The Heart

1. The Heart

2. The Heart • right pulmonary arteries • semilunar valves • right atrium • superior vena cava • right pulmonary veins • Inferior vena cava • septum • aorta • left pulmonary arteries • pulmonary trunk • left ventricle • left pulmonary veins • right ventricle • left atrium • atrioventricular valve

3. The Heart

4. The Heart

5. The Heart

6. Control of the Heartbeat • You cannot hold your pulse even for a single beat. • Your heart continues beating regularly if you are knocked unconscious, and may even continue beating for a while after you die. • The impulse that triggers the heartbeat actually originates from within the heart itself. • There are nerves (autonomic NS) that connect to the heart but they do not initiate or control the heartbeat • A cardiac cycle is defined as a complete cardiac movement, including systole, intervening pause, and diastole

7. Control of the Heartbeat • The contraction phase is systole, while the filling phase is diastole • A bundle of specialized muscle tissue, located in the wall of the right atrium, stimulates the muscle fibres to contract and relax rhythmically. • Thesinoatrial node (S-A node) = the pacemaker • Atria contract while ventricles relax, and the ventricles contract while atria relax. • Heart sounds are created primarily from turbulence in blood flow created by valves closing, not from contraction. • Why do heart sounds come in pairs?

9. Control of Heartbeat • The Atrioventricular (AV) node is also located on the right side of the heart, just beneath the surface of the interventricular septum. • The Bundle of His, is a band of nerve fibers that originates at the AV node, then passes along the interventricular septum to the ventricles. • The right and left bundle branches proceed along the right and left sides of the interventricular septum to the tips of the two ventricles. • The Purkinje Fibers are the tree-like terminal branchings of the right and left bundles.

10. Control of Heartbeat • After the SA node fires: • the electric signal spreads throughout the muscles of both atria • Atrium contract • The impulse then passes through the AV node to the Bundle of His • The signal is then divided between right and left bundle branches • When they reach the terminals of the Purkinje fibers they leap across to the cardiac muscle fibers • Ventricles contract • All this happens in less than a second.

12. Electrocardiographs (ECGs) • Represents (and measures) the electric activity of the heart • A normal ECG graph appears as follows:

13. An upward deflection of the wave represents an electric impulse traveling towards a sensor

14. ECGs • Each of the letters designates a different phase of the cardiac cycle. • P wave: generation of the electrical impulse at the SA node and its subsequent spread through the atria. • PR interval: During this interval the impulse travels through the atria and the AV node.

15. ECGs • QRS complex. The time necessary for the impulse to spread through the bundle of His and its branches to complete ventricular contraction • ST segment. The ST segment represents the period between the completion reversal of charges in the ventricular muscle tissue. • T wave. The T wave represents the return to normal state of ventricular muscle tissue that occurs after ventricular contraction.

18. Chemical Regulators • When you are relaxed, your S-A node fires regularly • around 70 times a minute. • This firing rate adjusts, however, to meet your body’s needs. • Read the Chemical Regulators section on p. 305 • There are two negative feedback loops described • Fill in the worksheet with the appropriate information for each of these loops

19. Control of Heartbeat • Physical activity is not the only trigger for an increased heart rate. • The nervous system releases adrenaline when you are nervous, angry, or excited, or after a sudden shock or sharp pain. • “fight or flight” response: • a physiological change that prepares the body for anticipated activity • attack, defence, or escape. • As the heart rate increases, so does blood flow to the muscles, resulting in more oxygen being delivered to the muscle cells.

20. Adrenaline

21. Cardiac Output • The amount of blood pumped by the heart is often referred to as the cardiac output • = volume of blood pumped from each ventricle per unit of time. • a measure of the level of oxygen delivery to the body • Indicatesthe total level of work the muscles must perform • Two factors affect the cardiac output • heart rate (HR) = number of times the heart beats in a unit of time (minute) • stroke volume (SV) = the amount of blood forced out of the heart with each heartbeat cardiac output = SV × HR • Average person has a stroke volume of about 70 mL and a resting heart rate of about 70 beats per minute, for a cardiac output of about 4900 mL/min.

22. Cardiac Output • Out of Shape • Average • Extremely Fit

23. Cardiac Output • Individual A = Average • Individual B = Out of Shape, Unhealthy • Low stroke volume results in a high resting heart rate • Individual C =Exceptionally fit • very high stroke volume results in a low resting heart rate • can maintain the same level of oxygen delivery at a much lower heart rate than the less fit individual B. • Why is a low resting heart rate healthier? • When the heart is forced to work harder, it will break down sooner

24. ECGs Activity: • Research 1 of 3 other conditions on www.ecglibrary.com • left ventricular stenosis • atrioventricular block • Wolf-Parkinson White • Draw a normal ECG • Draw the abnormal ECG for the condition • Identify where the major differences are (which sections of the ECG) between the two ECGs • Explain the pattern and cause of the abnormal ECG

25. Blood Pressure

26. Blood Pressure